Spring - using static final fields (constants) for bean initialization

Question

is it possible to define a bean with the use of static final fields of CoreProtocolPNames class like this:

<bean id="httpParamBean" class="org.apache.http.params.HttpProtocolParamBean">
     <constructor-arg ref="httpParams"/>
     <property name="httpElementCharset" value="CoreProtocolPNames.HTTP_ELEMENT_CHARSET" />
     <property name="version" value="CoreProtocolPNames.PROTOCOL_VERSION">
</bean>

public interface CoreProtocolPNames {

    public static final String PROTOCOL_VERSION = "http.protocol.version"; 

    public static final String HTTP_ELEMENT_CHARSET = "http.protocol.element-charset"; 
}

If it is possible, what is the best way of doing this ?

Either delete the question or leave it as is, but not something in between. Thanks. — Pascal Thivent
– Pascal Thivent, Commented May 24, 2010 at 14:58

Community · Accepted Answer · 2014-11-21 01:29:00Z

115

Something like this (Spring 2.5)

<bean id="foo" class="Bar">
    <property name="myValue">
        <util:constant static-field="java.lang.Integer.MAX_VALUE"/>
    </property>
</bean>

Where util namespace is from xmlns:util="http://www.springframework.org/schema/util"

But for Spring 3, it would be cleaner to use the @Value annotation and the expression language. Which looks like this:

public class Bar {
    @Value("T(java.lang.Integer).MAX_VALUE")
    private Integer myValue;
}

edited Nov 21, 2014 at 1:29

CommunityBot

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answered May 24, 2010 at 14:54

Paul McKenzie

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6 Comments

Sampath Pasupunuri Over a year ago

also add the schema location xsi:schemaLocation=" springframework.org/schema/util springframework.org/schema/util/spring-util-3.1.xsd">

8bitme Over a year ago

Using Spring EL for your XML config this works: #{T(com.foo.Headers).HEADER_STATUS} as per jonstefansson.blogspot.com/2011/02/…

Gunjan Shah Over a year ago

How can we mark a field as private and final when bean is declared by Annotation ?

Blake Over a year ago

can you explain what the T(Type) does in your @Value annotation? I am unfamiliar with that notation. I've always used @Value("${my.jvm.arg.name}")

Ed Randall Over a year ago

I'm still struggling with the benefits of 'cleaner' annotations - the trouble with @Value is, you must re-release your code to change the configuration - wheras using XML you can separately re-release the config, or have different sets of configs, depending on environment.

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cr7pt0gr4ph7 · Accepted Answer · 2014-06-17 08:37:41Z

29

Or, as an alternative, using Spring EL directly in XML:

<bean id="foo1" class="Foo" p:someOrgValue="#{T(org.example.Bar).myValue}"/>

This has the additional advantage of working with namespace configuration:

<tx:annotation-driven order="#{T(org.example.Bar).myValue}"/>

answered Jun 17, 2014 at 8:37

cr7pt0gr4ph7

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Comments

Sampath Pasupunuri · Accepted Answer · 2014-03-17 22:13:04Z

12

don't forget to specify the schema location..

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:util="http://www.springframework.org/schema/util"
   xsi:schemaLocation="
     http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
     http://www.springframework.org/schema/util  http://www.springframework.org/schema/util/spring-util-3.1.xsd">


</beans>

answered Mar 17, 2014 at 22:13

Sampath Pasupunuri

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Comments

Balaji Boggaram Ramanarayan · Accepted Answer · 2015-06-05 23:17:18Z

6

One more example to add for the instance above. This is how you can use a static constant in a bean using Spring.

<bean id="foo1" class="Foo">
  <property name="someOrgValue">
    <util:constant static-field="org.example.Bar.myValue"/>
  </property>
</bean>

package org.example;

public class Bar {
  public static String myValue = "SOME_CONSTANT";
}

package someorg.example;

public class Foo {
    String someOrgValue; 
    foo(String value){
        this.someOrgValue = value;
    }
}

edited Jun 5, 2015 at 23:17

answered May 23, 2013 at 18:26

Balaji Boggaram Ramanarayan

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Comments

chetan singhal · Accepted Answer · 2016-05-24 06:54:42Z

2

<util:constant id="MANAGER"
        static-field="EmployeeDTO.MANAGER" />

<util:constant id="DIRECTOR"
    static-field="EmployeeDTO.DIRECTOR" />

<!-- Use the static final bean constants here -->
<bean name="employeeTypeWrapper" class="ClassName">
    <property name="manager" ref="MANAGER" />
    <property name="director" ref="DIRECTOR" />
</bean>

answered May 24, 2016 at 6:54

chetan singhal

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